malloc/tst-malloc-tcache-leak.c

   1 /* Bug 22111: Test that threads do not leak their per thread cache.
   2    Copyright (C) 2015-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 /* The point of this test is to start and exit a large number of
  20    threads, while at the same time looking to see if the used
  21    memory grows with each round of threads run.  If the memory
  22    grows above some linear bound we declare the test failed and
  23    that the malloc implementation is leaking memory with each
  24    thread.  This is a good indicator that the thread local cache
  25    is leaking chunks.  */
  26
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <malloc.h>
  30 #include <pthread.h>
  31 #include <assert.h>
  32 #include <libc-diag.h>
  33
  34 #include <support/check.h>
  35 #include <support/support.h>
  36 #include <support/xthread.h>
  37
  38 void *
  39 worker (void *data)
  40 {
  41   void *ret;
  42   /* Allocate an arbitrary amount of memory that is known to fit into
  43      the thread local cache (tcache).  If we have at least 64 bins
  44      (default e.g. TCACHE_MAX_BINS) we should be able to allocate 32
  45      bytes and force malloc to fill the tcache.  We are assuming tcahce
  46      init happens at the first small alloc, but it might in the future
  47      be deferred to some other point.  Therefore to future proof this
  48      test we include a full alloc/free/alloc cycle for the thread.  We
  49      need a compiler barrier to avoid the removal of the useless
  50      alloc/free.  We send some memory back to main to have the memory
  51      freed after the thread dies, as just another check that the chunks
  52      that were previously in the tcache are still OK to free after
  53      thread death.  */
  54   ret = xmalloc (32);
  55   __asm__ volatile ("" ::: "memory");
  56   free (ret);
  57   return (void *) xmalloc (32);
  58 }
  59
  60 static int
  61 do_test (void)
  62 {
  63   pthread_t *thread;
  64   struct mallinfo info_before, info_after;
  65   void *retval;
  66
  67   /* This is an arbitrary choice. We choose a total of THREADS
  68      threads created and joined.  This gives us enough iterations to
  69      show a leak.  */
  70   int threads = 100000;
  71
  72   /* Avoid there being 0 malloc'd data at this point by allocating the
  73      pthread_t required to run the test.  */
  74   thread = (pthread_t *) xcalloc (1, sizeof (pthread_t));
  75
  76   /* The test below covers the deprecated mallinfo function.  */
  77   DIAG_PUSH_NEEDS_COMMENT;
  78   DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wdeprecated-declarations");
  79
  80   info_before = mallinfo ();
  81
  82   assert (info_before.uordblks != 0);
  83
  84   printf ("INFO: %d (bytes) are in use before starting threads.\n",
  85           info_before.uordblks);
  86
  87   for (int loop = 0; loop < threads; loop++)
  88     {
  89       *thread = xpthread_create (NULL, worker, NULL);
  90       retval = xpthread_join (*thread);
  91       free (retval);
  92     }
  93
  94   info_after = mallinfo ();
  95   printf ("INFO: %d (bytes) are in use after all threads joined.\n",
  96           info_after.uordblks);
  97
  98   /* We need to compare the memory in use before and the memory in use
  99      after starting and joining THREADS threads.  We almost always grow
 100      memory slightly, but not much. Consider that if even 1-byte leaked
 101      per thread we'd have THREADS bytes of additional memory, and in
 102      general the in-use at the start of main is quite low.  We will
 103      always leak a full malloc chunk, and never just 1-byte, therefore
 104      anything above "+ threads" from the start (constant offset) is a
 105      leak.  Obviously this assumes no thread-related malloc'd internal
 106      libc data structures persist beyond the thread death, and any that
 107      did would limit the number of times you could call pthread_create,
 108      which is a QoI we'd want to detect and fix.  */
 109   if (info_after.uordblks > (info_before.uordblks + threads))
 110     FAIL_EXIT1 ("Memory usage after threads is too high.\n");
 111
 112   DIAG_POP_NEEDS_COMMENT;
 113
 114   /* Did not detect excessive memory usage.  */
 115   free (thread);
 116   exit (0);
 117 }
 118
 119 #define TIMEOUT 50
 120 #include <support/test-driver.c>